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An inherent instability study using ab initio computational methods and experimental validation of Pb(SCN)₂ based perovskites for solar cell applications.

ABSTRACT: Perovskite materials with ABX₃ chemistries are promising candidates for photovoltaic applications, owing to their suitable optoelectronic properties. However, they are highly hydrophilic and unstable in nature, limiting the commercialization of perovskite photovoltaics. Mixed halide ion-doped perovskites are reported to be more stable compared to simple ABX₃ chemistries. This paper describes ab initio modeling, synthesis, and characterization of thiocyanate doped lead iodide CH₃NH₃PbI_(3-x)(SCN)_x perovskites. Several perovskite chemistries with an increasing concentration of (SCN)^- at x?=?0, 0.25, 0.49, 1.0, 1.45 were evaluated. Subsequently, 'n-i-p' and 'p-i-n' perovskite solar device architectures, corresponding to x?=?0, 0.25, 0.49, 1.0 thiocyanate doped lead halide perovskite chemistry were fabricated. The study shows that among all the devices fabricated for different compositions of perovskites, p-i-n perovskite solar cell fabricated using CH₃NH₃PbI_(3-x)(SCN)_x perovskite at x?=?1.0 exhibited the highest stability and device efficiency was retained until 450 h. Finally, a solar panel was fabricated and its stability was monitored.

SUBMITTER: Dutta J

PROVIDER: S-EPMC7498586 | biostudies-literature | 2020 Sep

REPOSITORIES: biostudies-literature

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An inherent instability study using ab initio computational methods and experimental validation of Pb(SCN)2 based perovskites for solar cell applications.

Dutta Jayita J Chennamkulam Ajith Mithun M Dutta Soumya S R Kadhane Umesh U Kochupurackal B Jinesh J Rai Beena B

Scientific reports 20200917 1

Perovskite materials with ABX3 chemistries are promising candidates for photovoltaic applications, owing to their suitable optoelectronic properties. However, they are highly hydrophilic and unstable in nature, limiting the commercialization of perovskite photovoltaics. Mixed halide ion-doped perovskites are reported to be more stable compared to simple ABX3 chemistries. This paper describes ab initio modeling, synthesis, and characterization of thiocyanate doped lead iodid ...[more]

PMID: 32943649

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Project description:Hydrogen bonds (HBs) play an important role in the rotational dynamics of organic cations in hybrid organic/inorganic halide perovskites, thus affecting the structural and electronic properties of the perovskites. However, the properties and even the existence of HBs in these perovskites are not well established. In this study, we investigate HBs in perovskites MAPbBr3 (MA+ = CH3NH3+), FAPbI3 (FA+ = CH(NH2)2+), and their solid solution with composition (FAPbI3)7/8(MAPbBr3)1/8, using ab initio molecular dynamics and electronic structure calculations. We consider HBs donated by X-H fragments (X = N and C) of the organic cations and accepted by the halides (Y = Br and I) and characterize their properties based on pair distribution functions and on a combined distribution function of the hydrogen-acceptor distance with the donor-hydrogen-acceptor angle. By analyzing these functions, we establish geometrical criteria for HB existence based on the hydrogen-acceptor (H-Y) distance and donor-hydrogen-acceptor angle (X-H-Y). The distance condition is defined as d(H - Y) < 3 Å for N-H-donated HBs and d(H - Y) < 4 Å for C-H-donated HBs. The angular condition is 135° < (X - H - Y) < 180° for both types of HBs. A HB is considered to be formed when both angular and distance conditions are simultaneously satisfied. At the simulated temperature (350 K), the HBs dynamically break and form. We compute the time correlation functions of HB existence and HB lifetimes, which range between 0.1 and 0.3 ps at that temperature. The analysis of HB lifetimes indicates that N-H-Br bonds are relatively stronger than N-H-I bonds, while C-H-Y bonds are weaker, with a minimal influence from the halide and cation. To evaluate the impact of HBs on the vibrational spectra, we present the power spectrum in the region of N-H and C-H stretching modes, comparing them with the normal mode frequencies of isolated cations. We show that the peaks associated with N-H stretching modes in perovskites are redshifted and asymmetrically deformed, while the C-H peaks do not exhibit these effects.

Project description:Molecular photoswitches that are capable of storing solar energy, so-called molecular solar thermal storage systems, are interesting candidates for future renewable energy applications. In this context, substituted norbornadiene-quadricyclane systems have received renewed interest due to recent advances in their synthesis. The optical, thermodynamic, and kinetic properties of these systems can vary dramatically depending on the chosen substituents. The molecular design of optimal compounds therefore requires a detailed understanding of the effect of individual substituents as well as their interplay. Here, we model absorption spectra, potential energy storage, and thermal barriers for back-conversion of several substituted systems using both single-reference (density functional theory using PBE, B3LYP, CAM-B3LYP, M06, M06-2x, and M06-L functionals as well as MP2 calculations) and multireference methods (complete active space techniques). Already the diaryl substituted compound displays a strong red-shift compared to the unsubstituted system, which is shown to result from the extension of the conjugated ?-system upon substitution. Using specific donor/acceptor groups gives rise to a further albeit relatively smaller red-shift. The calculated storage energy is found to be rather insensitive to the specific substituents, although solvent effects are likely to be important and require further study. The barrier for thermal back-conversion exhibits strong multireference character and as a result is noticeably correlated with the red-shift. Two possible reaction paths for the thermal back-conversion of diaryl substituted quadricyclane are identified and it is shown that among the compounds considered the path via the acceptor side is systematically favored. Finally, the present study establishes the basis for high-throughput screening of norbornadiene-quadricyclane compounds as it provides guidelines for the level of accuracy that can be expected for key properties from several different techniques.

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An inherent instability study using ab initio computational methods and experimental validation of Pb(SCN)₂ based perovskites for solar cell applications.

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An inherent instability study using ab initio computational methods and experimental validation of Pb(SCN)<sub>2</sub> based perovskites for solar cell applications.

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